1. Field of the Invention
The present invention relates to a drive control device that performs drive control of a plurality of loads based on PWM signals.
2. Description of the Related Art
Conventionally, drive control devices that perform drive control of electromagnetic actuators, such as motors or solenoids, using PWM signals have been proposed.
In particular, for a printing apparatus, such as an inkjet printer, including a paper transport system using a plurality of DC motors to convey printing paper sheets, a device to perform drive control of the DC motors by directly feeding a PWM signal to each DC motor has been proposed.
During drive control of a DC motor using a PWM signal, a drive current flows to the DC motor from a drive power supply that is connected to the DC motor for an ON period of the PWM signal. At this time, it is known that a so-called ripple current is generated when the pulse of the PWM signal rises and falls.
Then, in the case where the drive control of a plurality of DC motors is performed using PWM signals, as mentioned above, if the PWM signals fed to the individual motors have the same phase, for example, ripple currents are generated at the same time when the PWM signals rise and fall and the ripple currents are added, causing electromagnetic noise at the drive power supply. Further, in a case where a smoothing capacitor is provided to reduce influence of the ripple currents, it is necessary to provide the capacitor with a large capacity, and this results in cost increase.
In order to address this problem, Japanese Unexamined Patent Publication Nos. 2004-274974 (Patent Document 1) and 2005-176472 (Patent Document 2), for example, have proposed methods for reducing influence of ripple currents, where, during drive control of a plurality of loads using PWM signals, phases of the PWM signals fed to the individual loads are shifted from each other.